Shortness of breath that comes and goes| Some facts you should know.

You feel perfectly fine—and then suddenly you can't seem to get enough air. A few minutes later, your breathing may be back to normal. What could cause shortness of breath that comes and goes like this?

There isn't just one possible explanation. Problems involving the lungs, heart, digestive system, and even anxiety can cause breathlessness that comes and goes. Here are ten possible causes worth knowing about.

Asthma is an inflammatory condition of the airways that often causes symptoms that come and go. During an asthma flare, the airways narrow, their walls can become swollen, and mucus may increase. This makes it harder to move air out of the lungs and can cause shortness of breath, chest tightness, coughing, and the typical wheeze.

COPD is a chronic lung disease that commonly develops after years of smoking, although long-term exposure to other lung irritants can also contribute. Unlike asthma, COPD causes persistent airflow obstruction, but symptoms can suddenly worsen during periods called exacerbations. Respiratory infections are a common trigger for COPD exacerbations, bringing us to the next cause of intermittent shortness of breath.

Respiratory infections can happen to anyone. Most people are familiar with the common cold. This infection of the upper airways is not usually accompanied by shortness of breath. If, however, the infection spreads to the lower airways or lungs, shortness of breath can result. This is usually accompanied by a cough and other symptoms such as fever, chills, fatigue, or feeling generally unwell. These are clues to the infectious nature of the problem.

Heart failure is another relatively common cause of shortness of breath. People with heart failure can develop a buildup of fluid in and around the air spaces of the lungs. This congestion makes breathing more difficult and can cause a sensation of shortness of breath. Heart failure symptoms can improve and worsen over time. As fluid begins to accumulate, a person may notice increasing shortness of breath with activity, when lying flat, or even suddenly during the night. Common triggers of decompensation of heart failure are infections, a high-salt meal, or excessive sodium intake.

The next condition that can cause shortness of breath that comes and goes is coronary artery disease. When the heart muscle does not receive enough oxygen-rich blood, a person may develop angina. Although we often think of angina as chest pressure or discomfort, some people also experience shortness of breath. Sometimes shortness of breath may occur without chest pain and can represent what doctors call an anginal equivalent.

Arrhythmias, such as atrial fibrillation, can also cause a sensation of shortness of breath. Shortness of breath that comes and goes is particularly common in patients who have paroxysmal atrial fibrillation. During an episode of atrial fibrillation, the heart may beat rapidly and irregularly and may not pump as efficiently. This can cause palpitations, fatigue, dizziness, or shortness of breath. An EKG obtained during an episode may reveal the arrhythmia.

Anxiety and panic attacks can also cause sudden episodes of shortness of breath. A person may breathe rapidly and develop chest tightness, tingling around the mouth or fingers, dizziness, or a feeling that they cannot get enough air. However, these symptoms can overlap with heart and lung problems, so new or unexplained shortness of breath should not automatically be blamed on anxiety.

People who suffer from obstructive sleep apnea often awaken in the middle of the night gasping for air. If they are not aware of their condition, they can be surprised by it. They may attribute their symptoms to other causes. During an episode, the upper airway narrows or closes, temporarily reducing or stopping airflow. The resulting drop in airflow—and sometimes oxygen level—causes the brain to briefly arouse the person so that the airway can reopen.

Acid reflux and hiatal hernias can sometimes cause SOB that comes and goes. Acid reflux can sometimes contribute to coughing, throat irritation, wheezing, or a sensation of difficulty breathing, and it may worsen asthma in some people. Symptoms occurring after meals or when lying down may provide a clue. Large hiatal hernias can also occasionally contribute to shortness of breath, although this is much less common. However, reflux should not automatically be assumed to be the cause of unexplained shortness of breath.

Finally, obesity and physical deconditioning can make everyday activities require considerably more effort. A person may become short of breath while walking, climbing stairs, or performing other activities and then feel better after resting. However, shortness of breath should not automatically be attributed to weight or poor physical conditioning. Other important causes may need to be excluded first.

One important warning: Not every cause of shortness of breath belongs on a “most common” list. A blood clot in the lung, or pulmonary embolism, can cause sudden, unexplained shortness of breath and may be life-threatening. Sudden severe breathlessness—particularly with chest pain, fainting, coughing up blood, or a rapid heartbeat—requires urgent medical evaluation.

These are not the only causes of shortness of breath that comes and goes. Never try to diagnose the cause based on symptoms alone. If you have new, unexplained, or worsening shortness of breath, consult a healthcare professional so the cause can be properly evaluated.